Sponge rubber coated fabric and method of manufacturing the same



June 20, 1939. J. PENNEL ET! AL SPONGE RUBBER COATED FABRIC AND METHODOf MANUFACTURING THE SAME 2 Shets-Sheet 1 Filed Dec. 1, 1936 .l.'...!!!'r"" llllllllllllllllllllllllllllllllllll'lll:

Illlllllllllllllllllllllllllllllllllllll ..\..||.||||l|1|||..|.lIIIIIIIIIIIlllllllllllllllllllllllllllll JEAN PENNEL JOSEPH FL/po Z:QHEo-rneys.

June 20, 1939. 2,163,289

s ouem RUBBER COATED FABRIC AND METHOD OF MANUFACTURING THE SAME J.PENNEL EIAL Filed Uc.

l, 1956 2 Sheets-Sheet 2 n I I n n m. n I: a I a. I I I I I 0 l I I Mdltllllllllllll l 4141111114 11414411111, Ill

Patented Juneb2 0, 193 9 k O F E,

METHOD OFMANUFACTURING THE SAME Jean Pennel, ltoiibaix, and JosephFlipo, Croix,

' r France Application December '1, .1936, Serial No. 113,570 In FranceJune 4, 1932- 5 Claims. (CI. 91-70) This invention relates to spongerubber coated fabrics and to methods of manufacturing the same. 7

The present application is a continuation in 5 part of our co-pendingpatent application filed June 2, 1933, Serial No. 673,998.

Sponge rubber is generally made by mixing a mass of crude and masticatedrubber with substances capable of developing gases when sub- 10 jectedto heat, or by introducing gases under pressure into the rubber. Thenthe rubber composition is cut into sheets or pieces of suitabledimensions which are placed in molds between thep lates of a press or inan autoclave, where- 18 by the walls of the mold or the steam pressurewithin the autoclave regulate and limit the expansion of the gaseswithin the rubber, so that sponge rubber of predetermined dimensions andshape is produced. 7

20 Our preferred method of providing layers of sponge rubber of thistype on fabrics of all kinds, carpets, cardboard, paper, leather and thelike comprises the steps of mixing rubber with sulphur, accelerators,blowing agents, plasticizers,

fillers and coloring material, calendering the mixture on the web at atemperature lower than that at which the swelling agent commences to beliberated and festooning the sheet in an oven so that the rubberizedfabric will gradually be warmed through the swelling and vulcanizingtemperature range.

We found that the practical realization of the above and similar methodsof providing sponge rubber coatings presents certain difliculties anddrawbacks.

One of these drawbacks is that in prior art processes, particularlythose wherein latex is employed, charging agents, coloring substancesand the like must be added to the rubber mass in predeterminedquantities which can be varied only within a narrow range. Furthermore,charging agents of special'type must be used in connection with thoseprocesses. The process wherein a mixture containing dry 5 rubber iscalendered and then vulcanized in hot air and under atmospheric pressurehas the disadvantage that the calendering must be carried out at atemperature which is lower than that at which the blowing agentcontained in the rubber mixture begins to decompose. Ammonia bicarbonatewhich is generally used as a blowing agent has a decompositiontemperature which isas low as 70 C. In order to avoid exceedin thistemperature during the calendering the rubher must be previously madeplastic, either by a prolonged mastication, or by the addition ofplastifying agents or some other method.

The necessity of maintaining the layer of the rubber mixture in a veryplastic state up to the vulcanization is very inconvenient since thesoft 5 rubber cannot be supported anymore upon the surface of the fabricor other material. If the sheet of fabric is vulcanizedin a verticalposition the rubber will slowly flow downward forming pockets or flawswhich destroy the uniformity of 10 the swelling operations and may spoilthe article entirely.

Furthermore, the bubbles formed in the course of the swelling processmay break and collapse since the walls of these bubbles are not su'fli-15 ciently strong to resist pressure exerted upon them until thevulcanization has been completed and the material hardened.

A suggestion has been made to eliminate this drawback by maintaining therubber-coated g0 sheet in a horizontal position during the vulcanizationand thus avoid the flowing of the rubber layer. This however, isdisadvantageous in that the length of the article which can bemanufactured is considerably limited. Further- 25 more, it is notpossible to obtain a fabric which is coated on both sides with spongerubber by vulcanizing it in a horizontal position, since the lowerlayer, of the rubber mixture would flow in the course of thevulcanization. 30

Consequently, by using processes known heretofore, it was not possibleto manufacture on a commercial scale a fabric coated by layers of spongerubber, with the exception of fabrics carrying extremely thin layers ofrubber. In the 35 latter case surface tension or molecular attractionprevent the flowing of the rubber relatively to the fabric.

However, in the case of very thin rubber layers the swelling of therubber produces very small 40 and isolated cells so that themanufactured article is not, properly speaking, sponge rubber.

An object of the present invention is to eliminate these drawbacks andto provide a process through the use of which it is possible to manu- 45facture a fabric coated on one or both sides by substantially thicklayers of sponge rubber..

Another object is to eliminate the flowing of rubber and to make itpossible to vulcanize very large sheets of fabric in vertical positions.

A further object of the present invention is the provision of .a processby means of which it is possible to obtain in one single operationlayers A still further object is the provision of a multicolored spongerubber layer or a sponge rubber layer which has the appearance ofmarble.

. rubber containing charging agents, coloring matter and othersubstances, the relative amounts of which,as added in the course of themanufacture, may vary within a very wide range.

The present invention is based on the discovery that the flowing of thesponge rubber layers may be avoided by coordinating the processes ofvulcanization and of swelling. The rubber mixture, at the time of theswelling, should be of sulficient hardness to avoid the flow of themixture,

' and yet it should not be too hard so as not to interfere with theswelling process and the formation of the gas cells.

In order to attain the desired results it is also necessary to extendthe duration of the vulcanization process. Since vulcanization is achemical reaction it usually takes place much faster than the swellingwhich is a physical process. The swelling process takes usually acomparatively long time since it is necessary for the gases to overcomethe forces of inertia.

The above and other objects of the present invention may be realized bya method which comprises the simultaneous use of two accelerators,

one of which is active at a substantially low temperature and is used insmall quantities which are insuilicient to entirely vulcanize the rubberlayer. This accelerator makes the rubber mass harder without bringing itinto the state of polymerization in which it would be incapable ofchanging its form anymore at that temperature. The second accelerator isone which is active at a higher temperature, namely at the time when therubber mixture has already passed through the swelling stage and hasattained its final form.

Due to the progressive increase in temperature the second acceleratoracts after the first one and completes the vulcanization of the rubbermixture.

One of the important features of the present invention is, therefore,the use of two accelerators acting one after the other for the purposeof prolonging the vulcanization period and causing the vulcanization andswelling processes to be carried out simultaneously, and therebyavoiding the flowing of the rubber mass.

Since many accelerators, or pairs of accelerators, will not produce thedesired results, the election of the proper accelerators is of greatimportance. This selection depends primarilyupon that of the blowingagent, since it is advisable that the first, more rapid acceleratorshould become active shortly after the beginning of the swelling. Whenmaking the selection it must also be considered that the secondaccelerator can have an energizing effect upon the first accelera torand thereby lower the temperature of vul-- canization.

As the main blowing agent we prefer to use ammonia bicarbonate whichbegins to decompose and form gases at a temperature of 70 C.Consequently the swelling of the rubber mixture con-' taining ammoniabicarbonate will begin at approximately the same temperature. Then it isnecessary to select such accelerators that the vulcanization willcommence at about 80 C. or'

s We have found after considerable experimentation that as the first,more rapid accelerator, it is advisable to use one belonging to thegroup of tuads or thiourea, provided that the second accelerator used'isone belonging to the group of mercaptans.

It is also necessary to carefully determine the amount of acceleratorsused in order that the first accelerator should not produce a too strongvulcanization. The total amount of the two accelerators may be about0.6% of the entire gum in the rubber mixture. It should be noted,however, that the proper selection of the amount of the accelerators inthe rubber mixture is also dependent upon the relation of the amount ofthe gum to the amount of the total mixture.

As already stated the amount of the first accelerator used should besuch that it will not be able to produce complete vulcanization. In factit is advisable to use about one-third or onefourth of that amount ofthe first accelerator by means of which complete vulcanization may beobtained.

As already stated, the accelerators are added to the rubber mixtureshortly before the calendering. The calendered rubber layer is graduallyheated, the swelling and the'vulcanization taking place as the result ofthis heat treatment.

When described accelerators are used in stated quantities thevulcanization takes place progressively between the temperatures of 85C. and 135 C.

It is evident that the temperatures used in the course of the heatingprocess and the extent of this heating process depend'upon the swellingtemperature and the action of the two selected accelerators.

In general the temperature should not rise too rapidly or too slowly inorder that each change in thephysical structure of the mixture shouldhave time to develop fully and should not be affected by varioussubsequent reactions.

It is easily possible for an operator to plot a temperature curve foreach individual case, provided that all necessary data are given. Suchcurve should preferably comprise intervals of about 10 or minutes eachduring which a uniform temperature is maintained. The propertemperatures of the heating process should be determined by taking underconsideration the chemical inertia of the products, the degree ofplasticity of the rubber mass and the time required for distributingthe'temperature equally throughout the interior of the mass.

By way of example the following data may be given:

A rise of temperature of the rubber mass from C. to 70 C. should takeplace in 13 minutes.

A rise of temperature from 70 C. to 110 C.

should take place in minutes. a

A rise of temperature from 110 C. to 135 C. should take place in 20minutes.

Obviously, the periods of time and temperatures should be changed tosuit the individual requirements.

In the course of the heating process the swelling will commence usuallyat about C. The

flowing agents will begin todecompose at that temperature and willcontinue to develop gases until a temperature of about C. or C.

Then a slight swelling and a slight softening of the mass will takeplace. vulcanization begins at about 85 C. and continues simultaneouslywith the increasing swelling and the increasing pressure of the gases.

In general, through the use of the described process, the swelling iscompleted in about one hour and the flow of the rubber or the formationof pocket flaws or tears, in the rubber coating is eifectivelyprevented.

The invention will appear more clearly from the following detaileddescription when taken in connection with the accompanying drawingsshowing by way of example, preferred embodiments of the inventive idea.

In the drawings:

Figures 1 and 2 are diagrams showing the apparatus employed for thecalendering and vulcanization operations, respectively.

Figures 3 to 9 are sections through articles manufactured in accordancewith the principles of the present invention.

As already stated, the process comprises three main operations whichare: the preparation of the mixture, the calendering and thevulcanising.

To prepare the mixture, the dry gum is first treated in a mixer in theusual manner and then plastifying agents, coloring materials, adjuvantsand blowing agents are added to it; the latter must be added at atemperature which is lower than that at which their decompositionbegins, such as 70 C. in case of ammonia bicarbonate. The acceleratorsare added to the mixture just prior to the calendering at a temperaturewhich also should be lower than the decomposition temperature.

The following examples of a rubber mixture are given by way ofillustration only. The contents of these mixtures may be varied whenevernecessary to suit individual requirements.

First example This mixture may be used for obtaining colored spongerubber layers of soft consistency:

Mixture used for obtaining white substantially firm sponge rubber.

Gum, crepe first-latex 50 Plastifying agents Palm oil 3 Vaseline 3Adjuvants, etc.

Zinc oxide 6 Lithopone 20 Ultramarine 0.2 Barium sulphate 16Accelerators.

Tetrone A (Thiuram tetrasulfide) 0.4 Zenite (Captax zinc salt) 1.25

Blowing agent, ammonia bicarbonate 3 The calendering of the above orsimilar mixtures is carried out first by softening the mixture and thenplacing it at M (Fig. 1) between the top cylinders or rollers A and B.The rubber mixture is drawn in and rolled between these two rollers,'thetemperature of which must be suitably regulated and must remain belowthe swelling point. The rubber mixture forms a film the thickness ofwhich may be varied by varying the space between the rollersA and B.This space may vary, for example, between 0.05 mm. and

The speed of the rollers is regulated in such manner that the rubbermixture. film winds itself around the middle cylinder B. Then the fabricT or the like which has the form of a band and which is wound over theroller D behind the cal ender is passed between the two cylinders B andC. The fabric or support T may be of different widths or thickness. Thedistance between the cylinders B and C is so adjusted that they willexert a pressure upon the fabric or support which will cause the film ofrubber mixture to adhere to it. The fabric T carrying the rubber layer Mis moved over a talcing table F and is wound upon a roller E. Then thefabric is cooled for a predetermined period of time. a

Thereupon the vulcanization operation is carried out by arranging thematerial in folds in a hot air oven (Fig. 2) consisting of a heatinsulating chamber H provided with steam pipes G which heat the chamberto the desired temperature. This type of oven makes it possible tovulcanize a large quantity of rubber-coated fabric in one singleoperation, the fabric being arranged upon rollers R in the form of foldsP. Then the doors and other apertures of the oven are closed and thechamber H is graduallyheated in accordance with a time-temperature curvewhich may be determined experimentally in advance.

It is advisable to carry out this heating in the each phase.

The following time-temperature relationship' was found to be suitablefor the mixture described Second phase: temperature increased from 70 to110 C. in 20 minutes.

Third phase: temperatureincreased from 110 C. to 135 C. in 15 minutes.

The mixture increases from three to four times in volume as a result ofthis treatment.

This finished product is rather firm and has a numberof small isolatedpores.

Figures 3 to 9 of the drawings illustrate several sponge rubber coatedfabrics manufactured in accordance with the described or similarmethods.

Figure 3 shows a fabric T covered by a layer of cellular or spongerubber C the thickness of which may vary between 0.2 millimeter and 20millimeters.

Figure 4 shows a fabric T one of the surfaces of which is covered by alayer of sponge rubber C while its other surface is covered by a layerof plain rubber c.

Figure 5 shows a fabric T the two surfaces of which are covered bylayers of sponge rubber Cf. Obviously, the two layers may be of the sameor different thicknesses.

Figure 6 shows a fabric T one of the surfaces of which is coated by aplurality of layers C 0'. Each of these layers may consist of a layer ofsponge rubber of the same or different consistency than another layer ofsponge rubber. It is also possible to combine a layer of sponge rubberwith one or more layers consisting of plain rubber.

Figure 7 shows a fabric '1 one of the surfaces of which is covered by alayer of sponge rubber C', while the other surface is coated by one ormore layers 0' c consisting of sponge rubber which may be of the same ordifferent consistency as the layer of sponge rubber C.

Figure 8 shows two fabrics T and T which are interconnected by a layerof sponge rubber C of any desired consistency.

Figure 9 shows two fabrics T and T the inner surfaces of which areinterconnected by a layer of sponge rubber C while their outer surfacesare coated by one or more layers C c consisting of plain or spongerubber of the same or different nature than the layer or sponge rubberC.

Sponge rubber used in all these articles may be of. different grainstructure or consistency These variations may be obtained by changingthe composition of the grain mixture, by varying the methods ofmanufacture or by varying the period of time during which the article iscooled between the calendering and the vulcanization.

By thedescribed methods it is possible to eliminate the use of molds,presses, autoclaves and the like and to manufacture on a commercialscale sponge rubber coated fabrics of great length and width, the layersof sponge rubber being uniform, of any desired thickness and devoid ofany flaws or pockets.

Several changes may be made in the described invention within the scopeof the appended claims. For example, accelerators of any type may beused, provided that the chemical reactions of the accelerators are suchthat the temperatures of the vulcanization of the rubbermixture willcorrespond to those at which the swelling agent will be decomposed.Accelerators which have been previously mixed, may be added in the formof such mixture to the rubber mixture. The important feature in theselection of the accelerators is the possibility of regulating thevulcaniration, so that it is carried out progressively andsimultaneously with the swelling, thereby avoiding the flowing of softrubber along its support. which otherwise might take place between theswelling and the vulcanizing operations.

What is claimed is:

l. The method of manufacturing a sponge rubber coated fabric and thelike, which com-- prises adding a swelling agent to a rubber mixture,

said swelling agent developing a gas within a predetermined range'oftemperatures adding to the mixture at least one accelerator the criticaltemperature of which is situated within said range of temperatures,applying the mixture in the form of at least one layer upon a pliablesheet and simultaneously calendering it, and then heating the mixture-in three separate stages from a temperature which is lower than 70 C.to a temperature of about 135 C. to cause a swelling and a vulcanizationthereof, whereby said swelling and said vulcanization take placesubstantially simultaneously.

2. The method of manufacturing a sponge rubber coated fabric and thelike, which comprises adding a swelling agent to a rubber mixture, saidswelling agent developing a gas within a predeterminedrange oftemperatures, adding to the mixture at least one accelerator thecritical temperature of which is situated within said'range oftemperatures. applying the mixture in the form of at least one layerupon a pliable sheet ,and

- simultaneously calendering it, suspending said sheet substantiallyvertically, and then heating the mixture by heat exchange with a heatedgas in three different stages, first to about 70 0., then to about 110C., and finally up to about 135 C. to cause a swelling and avulcanization thereof. whereby said swelling and said vulcanization takeplace substantially simultaneously, and a flowing of the mixturerelatively to said support is avoided, and whereby large sheets coatedby sponge rubber layers having a thickness ranging between 0.2millimeter and millimeters may be produced.

3. The method of manufacturing a sponge rubber coated fabric and thelike, which com-- prises adding a swelling agent to a rubber mixture,said swelling agent developing a gas within a predetermined range oftemperatures. adding two accelerators to the mixture, the criticaltemperature of one of said accelerators being substantially lower thanthe critical temperature of the other one of said accelerators, thecritical temperatures of both of said accelerators being situated withinsaid range of temperatures, applying the mixture in the form of atleastone layer upon a support, suspending the coated support, heating it upto about 70 0., then heating it to about 110 C., and finally heating itto about 135 C. to cause a swelling and vulcanization of said layer.whereby said swelling and said vulcanization take place substantiallysimultaneously and a flowing of said layer relatively to said support isavoided.

4. The method of manufacturing a sponge rubber coated fabric and thelike, which oomprises mixing ammonia bicarbonate with rubber gum, aplastifying agent and a charging agent. adding thiuram tetrasulflde andmercaptobenzothiazole zinc salt to the mixture, applying the mixture inthe form of at least one layer upon a support at a temperature lowerthan 70 (2., suspending the coated support, and then heating it in threeseparate stages to at least 135 C.to cause a swelling and vulcanizationof said layer.

5. The method of manufacturing a sponge rubber coated fabric and thelike. which comprises mixing ammonia bicarbonate with rubber gum, aplastifying agent and a charging agent, adding an accelerator belongingto the group consisting of tuads and thiourea, adding anotheraccelerator belonging to the group consisting of meroaptans, applyingthe mixture in the form of at least one layer upon a support at atemperature lower than 70 C., suspending the coated support, and thenheating it in three separate stages to at least 135 C. to cause aswelling and vulcanization of said layer.

' J. PENNEL.

J. mo.

